1. Field of the Invention
The invention relates to the field of batch fabricated micromachined gyroscopes and more particularly to batch fabricated micromachined rate integrating and angular rate gyroscopes and more generally to microscale spherical resonators.
2. Description of the Prior Art
The recent market survey of today's inertial sensors suggests the increasing demand for portable low-cost, and high-precision gyroscopes for communication systems, civil and military navigation. The gyroscopes can be classified into two major types: rate integrating (type 1) and angular rate (type 2). The type 1 gyroscopes are typically isotropic oscillators, which transfer energy between the normal modes of vibration (alternatively, principal axes of elasticity) when subject to inertial rotation. The intrinsic property of such resonators is the precession of the vibration axis in response to the inertial input, with the precession angle proportional to the rotation angle. When gyroscope of type 1 is implemented in the form of a vibrating axisymmetric solid body (for example, a shell), the elastic wave propagating in a body is used to directly measure the angle of rotation.
One implementation of the isotropic oscillator concept, the quartz hemispherical resonator gyroscope (HRG) demonstrates the potential of rate integrating gyroscopes (type 1) with inertial and higher grade performance. A disadvantage of the current technology for HRG is its extremely high cost, mainly due to a boutique manufacturing process. Although conventional HRG is widely used for precision inertial navigation and guidance applications, it is not suitable for man portable application because of its size, weight and power (SWaP) metrics.